1. Field of the Invention
The invention presented here has the object of a probe notably for ultrasonic scanning, which can be mainly used in dermatology, provided with an electroacoustic monotransducer driven by a back and forward movement in an acoustic coupling medium.
2. Description of the Related Art
Mechanical probes for ultrasonic scanning, generally consisting of a tubular body, can be gripped by hand and consist of a chamber in which an electroacoustic transducer is installed. To this tubular body, in the extension of the chamber, a tip of the probe is connected and provided with a slot for the passage of acoustic waves emitted by the transducer. Finally, a coupling medium such as a homogenous liquid is placed in the chamber. This liquid forms the propagation medium to the slot of the probe tip of ultrasonic waves emitted by the electroacoustic transducer. The slot of the probe tip is generally in the form of a more or less thin wall impermeable to the coupling liquid but permeable, in varying degrees, to the acoustic wave. In other devices, notably those specifically designed for scanning the skin and more generally for scanning at low depth, the slot of the probe tip is in the form of an opening. The reason for this arrangement is essentially that the scanning at low depth requires an ultrasonic wave at a higher frequency and that this wave is very easily attenuated by the wall of the slot. However, it should be known that most pathologies become located on the face in the zones which can be jagged, such as the nose and the lobe of the ears. For this reason, the use of a probe with an open acoustic slot can pose numerous problems such as that of keeping constant the quantity of the acoustic coupling liquid in the probe. The use of a wall, for example, in the form of a membrane to constitute the acoustic slot (preferred solution among practicing doctors) creates the problem of the attenuation of the wave and the repetition echoes between the slot and the acoustic transducer. These repetition echos are often a product of artifacts masking useful information and making it impossible to interpret the images. This problem can be solved if the acoustic beam is oblique relative to the slot as instructed in the prior art. In this case, the reflection echo is no longer sent back towards the acoustic transducer and the artifact no longer appears on the image formed. As a consequence, users have some problems in positioning the probe in a precise manner relative to the region to be scanned.
It is important that the signal coming from the probe be directly usable. Due to the pendular movement of the monotransducer, the output signal must be handled by a system having a format change. Such a system has the disadvantage of slowing down the display rate and reducing the size of the input slot.
Finally, due to their high frequencies, the return signals are easily damaged by the different zones crossed, land notably by the coupling medium.
The purpose of the invention presented here is to solve the problems mentioned above by implementing a new type of ultrasonic scanning probe designed to emit an output signal that can be used immediately in order to form a rectangular image.
Another purpose of the invention presented here is to propose an acoustic probe in which the slot of the tip of the probe is made up of a wall and whose acoustic beam is normal to this slot for an, easy positioning without artifacts being able to appear in the image formed.
Another goal of the invention presented here is to propose a probe for which the attenuation of the return signal in the coupling medium is reduced.
For this purpose, the low depth scanning probe, consisting of a tubular body in which a main chamber is arranged to accommodate an assembly for the emission and reception of an ultrasonic wave formed from an acoustic monotransducer, installed on a mount driven in a back and forth movement in the main chamber by a movement transmission united with a drive motor mounted in a secondary chamber arranged in the tubular body and separated from the main chamber by a partitioning element, the main chamber being blocked in an airtight manner by a probe tip that contains an acoustic slot made of a solid element, impermeable to the acoustic coupling liquid introduced into the main chamber and permeable to the acoustic wave emitted by the transducer in the direction from the anatomical region to be scanned and permeable to the return wave reflected by the anatomical region in the direction of the acoustic monotransducer, characterized essentially in that the back and forth movement of the assembly for the emission and reception of the acoustic wave is a movement in parallel translation to the acoustic slot of the probe tip, the ultrasonic beam staying normal to the slot of the tip of the probe.
By this device, the signal coming from the probe can be used directly so well that no mechanism for changing the format is required for the formation of a rectangular image that can then be displayed at a higher rate.
According to another characteristic of the invention, the distance between the assembly for the emission and reception of the acoustic wave and the acoustic slot is equal to or greater than: Pmax.c1/c2
where:
Pmax is the maximum depth of scanning
c1 is the speed of the acoustic wave in the coupling medium,
c2 is the speed of the acoustic wave in the anatomical region to be scanned.
This particularly advantageous arrangement of the invention eliminates any risk of an artifact in the image formed and guarantees a good distinction of the structure of the dermis and epidermis.
According to another characteristic of the invention, the coupling medium is essentially water.
This device eliminates the risk of al large attenuation of the signal.